Fireplace construction



Feb. 4, 1958 R. K.\'rHuLMAN `FIEREPLACEJ CONSTRUCTION 6 Sheets-Sheet 1 Filed'nec. 31, 1954 1N VENTOR v wm/V- maw/WV,

R. THULMAN FIRII-LACE CONSTRUCTION Filed Dec. 31, 1954V 6 Sheets-Sheet-Z IN VENTOR l Feb. 4, 1958 R. K. THULMAN FIREPLACE CONSTRUCTION Filed Dec.

6 Sheets-Sheet 3 IMIWIWIH INVENTOR Paar/P7- M 77E/amy@ Feb. 4,1958 l R. K. THULMAN FIREPLACE CONSTRUCTION 6 Sheets-Sheet 4 Filed D90. 3l, 1954 INVENTOR Feb. 4, 1958 R. K. THULMAN FIREPLACE CONSTRUCTION 6 She'ets-Sheet 5 Filed Dec. 31, 1954 INVENTOR Feb. 4, 1958 R. K. THULMAN 2,821,975

FIREPLACE CONSTRUCTION Filed Dec. 3l,- 1954 6 Sheets-Sheet 6 United States Patent() This invention relates to the art |of fireplace construction and more particularly to a iireplace which may be factory built and installed as a unit -at a home site without the `services of `skilled artisans. The invention is intended primarily for use in one and two story dwellings for the burning of fuels ordinarily used, such as wood,coke, charcoal and coal.

Among the objects of the invention are the provision of a fireplace which is safe, which stores little heat, unlike the massive masonry replaces of the prior art, which is non-smoking, light weight, economical, andpleasing in appearance. The fireplace of the present invention heats up quickly and produces a draft with only a small amount of heat. It is quick cooling, Vthereby reducing the ow of air from the house up the chimney and reducing the long periods of heat loss which accompany the use of conventional masonry fireplaces. The lireplace flue may be completely separate from the central heating plant ue, thereby obviating erratic behavior of the latter due to external heating, as is the casewhere Iboth the heating plant ue and the fireplace flue are enclosed in the same masonry chimney. The invention requires little space and is unrestricted in its location in the dwelling. It may be employed with its own chimney, but, .if desired, the fireplace chimney and the central heating plant chimney may terminate in a single top housing.

A primary `object of the invention is to provide a replace which does not cause auxiliary convection heating, as is the case with circulating fireplaces, 'and which thus does not upset the balance of the central heating system. In conventional installations, heat circulated from the fireplace may actuate the thermostatic control of the central heating system, thereby preventing the latter from operating and allownig rooms remote from the lireplace to cool to an undesirable degree. The heat output of the Iinvention to the adjoining room is principally by radiation.

The fireplace of the present invention may be employed most conveniently in conjunction with the chimney construction described and claimed in my prior Patent No. 2,634,720, issued` on April 14, 1953. In that patent, a chimney construction is described which utilizes thermosyphoni-c principles to control bothV the lateral and longitudinal heat gradient. The fireplace of the present invention also employs thermo-syphonic movement of air to maintain safe temperatures on the surface of the outer casing of the tireplace unit. syphonic paths are provided. All of the basic construction may be of metal, and the prevention of excessive temperatures on those surfaces in contact with combustible construction adjoining the fireplace may be ensured principally by thermal circulation of air and partially by the use of reflective surfaces. The fireplace and flue may be installed with zero clearance to combustible construction. The lireplace is a free standing assembly which also supports its flue and may be installed on and adjacent, to wood frame construction. Hearth extensions of the liush, stepped, 0r raised cantilever type may be em- A plurality of thermolCe 2 ployed, and a variety of face treatments with and without mantels may be provided.

In general the fireplace of the present invention may be formed as a single assembly comprising three basic elements." The tire box or lireplace proper may be a steel box lined with refractory surmounted by a pyramidal smoke chamber terminating in a circular outlet to which the smoke-flue of my aforesaid prior patent may be connected. The front sides and back of the fireplace may be welded or otherwise secured to a steel base plate. An inner liner or casing of light gauge metal and of substantially the same general shape as the fire box may be supported by welded steel brackets and spaced away from the replace and away from the base plate. The pyramidal section of the inner liner-may terminate in a circular opening spaced away from the ue gas conduit outletrso as to form anannular opening. The inner duct of the chimney of my aforesaid patent may be connected to this opening. A rectangular outer casing may surround the entire assembly Iof the lireplate and may be attached to the base plate. In the top of the outer casing is a circular opening, which lforms a second annulus with the opening in the inner casing. To this opening the outer duct of my chimney may be attached. Steel angle sections may be welded to the three sides of the combustion chamber slightly above the bottom edges to supp'ort a steel hearth section. The two front corners of the hearth section may be cut out so as to provide a pair of openings between the sides of the combustion chamber and the edges of the hearth. Between the hearth and the base plate a battle of aluminum or other suitable reflective material may be employed to divide the space under the hearth. This baille, at its back edge, may be shorter than the hearth so -that the space between the base` plate and the bae communicates with the space fbetween the b-ale and the under side of the hearth. A vertical extension of the baffle closes the front of the upper of these two Two vertical steel side dues or risers, which may The foregoing and other objects of the invention will become more apparent in the following detailed description of illustrative embodiments of the invention taken 1in conjunction with the accompanying drawings wherein:

Figure l is a general perspective view of a fireplace construction fully installed and ornamented in a typical manner;

Figure 2 is a perspective view of the lire box thereof mounted on the baseplate and provided with refractory lined hearth and interior surfaces;

Figure 3 is a perspective view of the inner casing thereof;

Figure 4 is a perspective view of the outer casing thereof;

Figure 5 is a perspective View of an embodiment of la steel riser employable therein;

Figure 6 is an loffset front sectional view taken along line 6 6 in Figure 7 and illustrating the assembled replace;

Figure 6a is a detail of Figure 6 on an enlarged scale;

Figure 7 is a side sectional view taken :along line 7-7 in Figure 6;

Figure 8 is a front elevation View of the assembled fireplace;

Figure 9 is a plan sectional view taken along line 9 9 in Figure 8;

Figure l0 is a perspective view of one form of-hearth (unlined) that may be employed in the construction;Y

Figure 1l is a modified sectional detail illustrating a typical manner of installing the fireplace in conjunction with au ornamental surround;

I'iig'u're 12 'is a'modifid sectional detail illustrating the manner of employing an ornamental hearth extension in conjunction with the fireplace; l

Figure .13 eis aperspectixe. view..of an.a1ternativefor n1,.-.t of riser which may 'be employed insteadof,;that..ill`u&.,...iV trated in FigureS;

Figure. ..14` is. a. sectionalfrv'iewi.ofan..a1ternative..5:on=z struction employing a smokescoopa additionaLbales anch,... a slightly. moditiedconstructiom.

Figure is; a froht,.sectional. view z takenalong-sline.. l0 15`15 in Figre...1 4 andiurthenillustratngthe:alterna: tive construction-lof that figure;

Figure 16 is an .il1us"trative..diagrameindicating theopf, e eration .of the @smoke scoop.-.under certain circustances;. Y

Figure l7 'is` another.illustrative..diagram,indicatingthew-f15 operation of thejsmokescooprunder other..circumstances;d and Figure 18 'isga ,broken away .perspective view` of the. assembly Vof` Figures .1-4-.17 .i1lu'strating,.the .plurality of.. gas flow pathsi 20 Referring to Figure' .1' ofthe dawing,. a typicaLins'tale lation of the'treplace `of'their'ivention mayinclude an. ornamental surround ory facing :.10 y of. .suitable material,..., for example marbleor ceramic.'tile,a hearth y 1-1,.and .a. hearth extension .12,"j which 1 i'nay,1 be .forined. ofsimilar ..25 material. vThe rear. face andthe sloping .side faces .of the tire box may .be .lined with'refractory. blo cks;16,.and.. the hearth may beilld"v`vith.a castable, ceramicmate-I. rial as indicated at 1'85.' The overallyppearanceof the.-. assembled fireplace unit may..,be`qui te'` closeto .the ap-...so pearance of conventional ,masonry installations.... The"V front opening of'f'the fire box maybe substantially'liushf with'an interior Wall 14;V while' the bottom surface off the fire `box'mayberaisetl above or ush withthe floor. surface 20'as desired. The exact manner of ii'lstallatiol't...35 is subject -tov innumerable' '.variations. It y.will besnoted thata slot`22i's formed'iirthe'front surface of the`hearth extension; and' the purpose of'thislslot willb'e'come more apparent hereinafter.`

The'generaliappearance of the re box unit'prior tol .10 assemblyand' installationis shown'in Figure 2:" The fireplaceissupportedona ba'se plate 24',which may bea sheetof-fsteelfwithturnedd'own'edges 26'.'Vv .Support legs v maybe spot welded to the bottom surfacerof the based. plateat strategic'points'asjndicated' at' 28 inFig'ures 6"45 and 7- to `supportthe iweight'of the zreplace.

Still referringrto' Figure- 2,' 'thegenera'L-shape of.' the." fire box'may `be substantially'llikthat'of'a conventional.i1 fireplacerl Itssides/ may'lp'etapered towardtheea-r and e providedA with*A straight side ex tensions 32 "havingfj 50 notches 34 at their lower front corners to accommodate.'- hearth 'extension-12. I' T h'e side' "andcbackfsurfac'es 4ofthe fire box'may belined-withl ceramic blocks asin'dicated' above so as to retain heat-ir1-the fire` Achamberitu-pro?L videal'ag' i'n-icoolingwhen the''re dies-down:l A pyramE 55 idal flue-communicating or smoke box section 36 extends. f' above ithe eiirevcha'tnbewand "terminatcsrin a* generaily circular outlet 38 to accommodate a flue 40. The ue, opening mayflbelcontrolledb'by avsuitable damper-39 (Figure 18). In practice, the ltop-\of'the'pyramidahsecf'60 tiontmay'terminatein a circulartcoupling, 'anda thesmoke ue of the prefabricated. chimney' deserbedin my' aforcsaid patent may be connected thereto or supported thereon atthe installation site: The back'fof the firecham` ber extends straight upwarda's shown-at 42 in Figure-`7f5 and the ceramic blocks 16 terminate at the beginning)i of the/pyramidal.` section as 4-seen2'-=at -44f-vinthat't'igurey so as to act as a vestigial smoke shelf. The flue cham-:t ber has a top extensionf iwhi'chfcloses'withk extensions 32 and is provided with a lip 33. 7

Tl1'e;hear.th, more vclearly-fillustratedeiny Figure 1:0, may be formedaof lightj gauge. steel-fandy is supported ouv-af plurality fof-steel angles 46iw'1eldedv ofthe`--rearand sides.; of theliire 'box as illustratedeihFlgures-6andl Their. 4 bottom of the hearth is thus raisedabovethesurfacc'of"75 the base plate. As seen in Figure 10 the hearth 11 may comprise a rear section 50 having tapered sides to complement the sides of the tire box and a front section 52 of slightly less width so as to form spaces 116 with side extensions 32, as shown in Figures 2 and 6. The rear portion 50 of the hearth may be formed from a single folded steel sheet (as shown.A in.. Figure 6), or may be formed from a at steel sheet-provided with a plurality of dividers 54,,whichf,may,.begsteekanglefstock secured as by welding to the bottom surface of the hearth (see Figure 10). As'indicatedl above, the sections of the hearth fmaybe filled with acastableceramic materialfl.

The inner casing, illustrated in Figure 3, comprises a rectangular bottomportionhaving sidewalls -56 and rear wall 58, and an upper pyramidal portion generally designated 60. The top of the pyramidal portion terminates in a circular opening to receive the inner duct or casing 61 ofathetchimney. above mentioned. Inpracticedhe top: of the pyramidal-portionrmay be provided]withacirculanm couplinggtsectiom..and the inner ductfontcasinghof theml chimneymay: beconnected; thereto orsupported thereon ft; at the. site of--installatiom Thefsides56; ofwithevbottomm portionareprovided.with a pair of'forwardlyeonverging nf extensions 62, the front edges of which are .formed :withe a pair,off.angularv -anges.;64... T he: forwardly extendingf. lipsgof;.theseangesfmay-.be notched at 66 solas.. tof-.comfplementxthe notches 34` of the tirer boxl illustratedinligure 2. h.The inner casing-is.provided;with a plurality-vof.. screw.holes.:68on each.,side.ft These holes ,receive bolts,. or sheetmetal..screws.which serve. to support, thefinnert casingfonbrackets 69 secured, preferably vby .weldingto the sidesofthere box (see Figure 2). whenthe-inner 1 casing ismountedonthefiref,box brackets,'it is spaced... from, the, fire box andraisedabove. the. base. plate..24..as.. illustrated in Figures 6, and 7.

The outer casing, ,i11ustrated iny Figure .4. comprises rean.wall .70,..sidewalls 71,v vertical front wal1s..f72 and. 74, rearwardlysloping front wally 76, anda top wall: 78..... Theitopis vprovided with a circularopening to receive.:v the outer ,ductor `casing of the chimney. v As set forth, withrespect to thefre box and inner` casing, Ia circular, coupling` section 8Lv (Figure v18) may be. providedand. the outer duct or casing of thechirnneymay be con-, nectedthereto or supported thereon at the ,site of instal-f. lation. The Vfrontal .opening of the. outer casing. is..pro. t vided".with'. an outwardlydirected. lip.Y 82,. the side .por-, tions of which[complement the." forwardly .extendinglips of flanges 64"of 'theinner casing (Figure13), andthe, top ,portion of which. complements lip 33 formed on .the extension 35of the'fire'box (Figure 2). 1, The. outer. cas. ing is designed 'totit 'about the downwardly turned lips.: 26 of. the' base plateas .seen in Figures 6 and 7, and. may bewelded. or. otherwise secured thereto and'when. assembled-"tlie'edges --of the frontal `opening in the, outer.4 casing-{close withj'the, correspondingf edges. of. the. fire box; rwhich;together with .the hearth define.V the.. access opening ofthe fireplace,...

'I"he-pian'o` hox shape of -the outer casing 68is particularlygadvantageous.. Frame partitions have a thick. ness 'ofapproximatelyjfive inches. ,Thus the-set b'acl{.oi.A the casing' immediate-ly above'the fireplace opening allows the `fran-ring around.` the' fireplace openingrto .be h'eldl down-to ar-reasonablef'height;and' minimizes the. area. necessary-to be coveredby the' surround^10 (Figure ,1);

Asshown in' Figures-6,661, and 7,"'thespace beneath' the `liearthe'and'aboverthefbase plate 'is divided 'into two parts-byahorizontal baie'84-having :a. depth. less than the depthJof'the.hearthrandfthe--frebox-so as to leave an opening`-86along-itsrear edge-(see :Figure 7 )forL como munica'ti'onbetweenthefspace above' andA below the baflic.

The-frontedges'ofthe'zbaierandthe base platevtogether Withtheifrontdges. of-thc fire boxdefine, a rectangular opening#88below'-theffront of'the hearth.k Theopening. which` would normallyexistA between y the bottom of; the

v heartlr'and thebaie" is closedbyrawupwardlyturned' lip 90 on the front edge of the baie, which may have a U shaped flange interlocking with the front edge of the hearth as indicated at 92 in Figure 7.

When a hearth extension such as extension 12 in Figure 1 is employed, the slot 22 therein is arranged to communicate with opening 88 below the baffle in Figure 7. Figure 12 illustrates the use of one such hearth extension, which may comprise a metal base plate 94, an upturned metal pan 96 supported on the base plate by suitable spacers 98 and filled with a ceramic material 100. The hearth extension may be provided with ornamental facing material as indicated at 102.

Baiiie 84 may be separated from base plate 2 4 by a plurality of spacer elements 104 and from the hearth by a plurality of spacer elements 105. The spacer elements are strategically arranged between the adjoining surfaces so as to support the weight of the fireplace and transmit this weight to the base plate. In practice the spacer elements may be constituted by U-shaped metal brackets spot welded to the under side of the hearth and the upper side of the base plate and insulated from batiie 84 by strips of asbestos tape 106 attached thereto in any suitable manner, preferably by cementing or stapling to the aluminum baie 84.

The sides of the fireplace opening as seen in Figure 1 are constituted by a pair of vertical risers 108, that are exposed to the radiant heat of the ire and induce iiow of cooling air under the hearth. Two exemplary embodiments are illustrated, one in Figure 5, and a second in Figures 13 and 14. In the form of Figure 5 the risers are preferably formed of stainless steel and have side surfaces 110, forward flanges 111 and rearward flanges 112. The risers are provided with outlet means, shown in Figure as slots 114 in their rearward flanges. The vertical risers are assembled against the inner surfaces of extensions 32 (Fig. 2) so as to form side flues communicating with the space above bailie 84 (Figures 6 and 7) through the spaces 116 formed between the ends of the forward hearth portion 52 (Fig. l0) and the side extensions 32 of the tire box. The assembly of the risers with the lire box may be clearly seen in Figure 9. As shown in this ligure, the forward anges of the risers complement the forward anges of the inner and outer casings as well as the forward extensions of the ire box, all of which may be secured together by U-shaped clamping strips 118 and metal screws or rivets (not shown). The rearward flanges of the risers together with the side walls 30 define rearwardly facing channels that serve to embrace the front edges of and retain the side fire block linings 16 in the tire box, and may be fixed to the extensions 32 of the iire box at 120 by metal screws. The side ceramic fire blocks 16 in turn may retain the rear fire blocks by engaging their edges as at 122. In the preferred form, all four of the ceramic blocks are interchangeable, and if one is broken, as by throwing a heavy log against it, replacement is simply made by prying out the rear edges of the side blocks, replacing the broken blocks, reseating the front edges of the side blocks, and swinging the side blocks back into position.

Figure l1 illustrates an alternative scheme for securing forward edges of the risers, tire box, and casings and at the same time aftixing an ornamental surround of glass, marble, tile, or other suitable material. In this gure the outer casing sidewall 71 is shown butted against a framing member 124, and the edges of the tire box, etc. are covered by an ornamental L shaped plate 125 and secured together and to the surround 126 by a pin or stud 127.

Figure 18 embodies some modifications yet to be described, but illustrates the plurality of. air paths formed by the assembly of the fireplace elements previously described. ln operation, flue gases from fuel burning on the hearth pass upward through. the line as indicated by arrows A. Heat from the liue is transferred to the air in the inner duct causing this air to rise as indicated by arrows B and be displaced by air descending freni the outer duct of the chimney and passing through the fireplace casings as indicated `by arrows C. The latter air passes downward through the outer casing of the replace along the rear and side Walls thereof and passes under the lower edges'of the inner casing and upward through the inner duct between the re box and the inner casing (arrows B). Air also passes down the outer duct between the frontal surfaces of the inner and outer casings and passes under the frontal edge of the inner casing at 128 (see also Figure 7). This air then passes up the inner duct and out the chimney. Some air also passes down the outer duct, across the top extension 35 of the lire box and up the inner duct as indicated by arrows C. The movement of air is thermosyphonic and is accelerated during heavy firing periods, thereby keep ing the outer surface of the fireplace unit cool, so that combustible material in contact with or adjacent to the fireplace is not endangered.

Another air path, indicated by arrows D, begins at opening 88 near the oor, continues in the space between the base plate and the lower surface of the baflle, around the rear edge of the baliie, into the space between the lower surface of the hearth and the upper surface of the battle, spreading transversely to openings 116, and then upward through the side lines formed by the vertical risers 108, into the tire box and up the central flue. Radiant heat from the fire heats the Vertical risers, causing the air in them to rise and be displaced by air from the frontal opening 88. This air, at room temperature, removes heat from the under side of the hearth and serves to prevent excessive temperatures on the floor under the fireplace. It will be noted that the riser structure 109 in Figure 18 differs slightly from that illustrated at 108 in Figure 5 in that the upper edge of the riser slopes downwardly and rearwardly to form the outlet means into the smoke chamber, thereby eliminating the surface of the tire box and to which the smoke scoop' is secured in any suitable manner, as indicated at 132. The smoke scoop terminates slightly rearward of the frontal edge of the re box and together with a depending lip 134 delines a slot 136 just within the re box opening. Lip 134, which may be constituted by a trim strip, may be welded or otherwise secured to the corresponding lips of the re box and outer casing. The trim and side liues are all replaceable elements. The trim strip in front of the smoke scoop can be replaced by a deeper one to regulate the size of the fireplace opening, or may be provided with a support for a drawtype screen if desired. The recessed front of the replace opening is adapted to receive a fire screen of the portable, portable folding type, or permanent hung curtain type.

The operation of the smoke scoop is illustrated in Figures 16 and 17. Under low draft conditions, smoke which might tend to diffuse into the room adjacent the fireplace opening is prevented from doing so as indicated in Figure 16 by air moving upward between the smoke scoop and the tire box upper wall. The air in the space thus deiined is heated by radiant heat from the tire box impinging on the smoke scoop 129, and rises upward into the central flue of the chimney` being displaced by cool air from the room moving into the slot 136 and carrying with it smoke at thefrontal opening of the replace. Under heavy smoking conditions, as shown in Figure 17, the air ow, in the smoke scoop may actually 'bis be reversed. .Under such conditions,,.however,ethe smoke is.drawn-back\into.`.the smoke .chamber bythe. draft on therel box .side of .the .warmedismoke scoop.,and .is prevented.fromitfusingintothe room.' By. intereepting r'adiant.heat, the...smoke. scoopi alsoreduces radiant heat-l ing.' ofth. frontal. surfaces .of ,the fireplace.

.'The .embodiment of .Figure 14 isl. also providedwith a pair of iauxiliary. blle's: 138, f1401n1ore`-clearly yillustrated in'l' Figure 15. fThese battles mayi assume-` generally. rectangular..forms. ande-be secured:'.underneathf` the sloping frontal surface' 76 of :the .outer casing., byA "anges ,}42. Biileflmaylhave substantially less .depth-tha'n baffle 140 iancLbenested within, thelatter. 'Thes'e baffles. serve to. reduce.'ev.en..further k the heatinglothe. frontalsurface of '.'the .outerr casing .by providing additionall airwblankets and. radiant. .heat.,interceptionbetwcenthe .outer .casing and the'ilirehoxas well as rac'lditicmalrelectivensurfaces.

"The fireplace of the presenttinventionr-ha`sbeen .tested and.approved by UnderwriterslLaboratories,` lncuras Fset forth. infits 'Miscellaneous HazardRepor-t" No: 6018,-Inly 14,.' 1954, .acopy'of Wh-ich. is.attached 'and'..incorporated hereinby reference. .ConstructionaL dimensions' and det'a'ilstare found in'i this report, vas `well` as desti-procedures and results. The.' latter establish'thatttherplaceldei) scribed 'will v'vithsta'nd extremeoverring aidyeh maintain the temperature. of the outerv casing AWell-'Within safe limits. Preferred.' forms fof.V the ,invention have beenldescribled herein more or. lessfpreci'sely` as..t6.de't'ai1s. .I't:is,.to be understood,` however, ,that th'efinvention is .not tb be .con si dered as limited thereby,.' ,that changes v.may l:be made in'the arrangementsand.proportions-fof parts, and-that equivalents may be substituted .'without'departing .from the s'pirit-and.scope Aof. the, invention.- It will.=be=.clear to those skilled! inithe .artl that' the. mannerifoh'shaping and assembling? ythe.variou s..parts i and `the' Vchoice vLof- .materials may be, subject to manyvariations.'fTheprimary parts` may be formed'of aluminiz'ed steel of suitablegauge, advantage being taken 'of its reflectiverpropertes to,` reduce even further heat .transfer ytoltheouter Vcasing,.a'nd the components may be. assembled. throghi the! ulseiof spot -Wlds," S-lockl strips, sheet .metal screws,..or `other appropriate means, It is 'therefore to vbe understoodethat the exemplary. embodiments are"illsti^ative and, not vrestrictive "of the invention',"thescope.of which.' isl .defined in the appended'claims,i.aid"that.'all 1moi'iiiicationsl'tlat. come'within the meaning andrangefof equivalency''fthe claims are' intended to b'e' inclnddjtherein.

" I claim as my invention:

outer casing'surroun'dingsaidiinner casingandQs'pacedf therefrom to Adefine" .an outer'zduct', sid"iner and ot'er ducts: communicating fadacen't'tlieir lower'extreiiitiesand having duct openings 'adaptedto 'communicate' withsid warm 'air an'd'c'old airchimneyducts,"respectively, 'whereforming-'therewithafveriiea1duet-communicating with saiid insaid'imfer 'casing being constituted by side 'extensions' having an upper terminus spaced below the top edge of the last mentioned frontal opening, said lire box having corresponding side extensions meeting the first mentioned side extensions.

9. A fireplace or the like in accordance with claim 5, said fire box having a hearth adjacent the bottom thereof, said hearth and at least part of the interior surfaces of the lower portion of said tire box being lined with refractory material, the material lining 'the rear wall of said fire box having au upper edge constituting a smoke shelf.

10. A fireplace installation comprising in combination, a prefabricated fireplace unit and a prefabricated chimney unit; said fireplace unit having a re box surrounded by inner and outer casings each mutually spaced from the others at rear, front, and sides to define inner and outer ducts around the re box, said fire box having a frontal opening and said outer casing having edges closing with the edges of the tire box at the top and sides of said frontal opening, said inner casing being formed to provide communication between said inner and outer ducts at the rear and sides of the fireplace unit adjacent the bottom of the unit and at the front of the fireplace unit adjacent the top of said frontal opening, said fireplace unit further comprising a central vertical smoke outlet extending upwardly from said re box, an annular air outlet concentric with said smoke outlet and communicating with said inner duct, and an annular air inlet concentric and surrounding said air outlet and communieating with said outer duct; said chimney unit comprising a central smoke ue tting said central smoke outlet,

and inner and outer air ducts open at their tops and fitting said annular air outlet and annular air inlet, respectively, whereby, on operation of the fireplace, a thermo-syphonic air circulation is induced in heat exchange relation with the lire box of the fireplace unit and the smoke flue of the chimney unit.

ll. A fireplace installation according to claim l0, said fire box supporting the smoke tlue of the chimney unit, said inner casing supporting the inner duct of said chimney unit, and said outer casing supporting the outer duct of said chimney unit, whereby the chimney load is divided between the said ireplace elements,

References Cited in the tile of this patent UNITED STATES PATENTS 289,634 Ernst Dec. 4, 1883 329,224 Sharpe Oct. 27, 1885 411,459 Lofts Sept. 24, 1889 474,655 Hart May 10, 1892 718,603 Chavasse Ian. 20, 1903 926,910 Taylor July 6, 1909 976,039 Cahoone Nov. 15, 1910 1,588,587 Klaus June 15, 1926 2,361,643 Mueller Oct. 31, 1944 2,642,859 Brown June 23, 1953 2,703,567 Manchester et al. Mar. 8, 1955 FOREIGN PATENTS 12,364 Great Britain Feb. 7, 1903 565,194 Great Britain Oct. 31, 1944 

